December 21, 2015

Because we can!

When total strangers meet…

Click on any image to see a larger version

What can you possibly expect when hooking up a camera, a lens and some accessories that were never intended to even meet? It would be rather foolish to presume that their individual designers worried for a moment about possible incompatibilities and unwanted interactions…

And yet, once in a while, the unexpected happens and you’re left with an intriguing combo to explore and enjoy!

Stage left: the Fujinon Teleconverter XF 1.4x TC WR

Last October, Fujifilm announced a 1.4x teleconverter adapter, a high-quality and high performance optical accessory that multiplies the focal length of the attached lens by 1.4x. As the imaging circle is enlarged (its surface area doubles) there is a one stop loss of light transmission. A series of firmware updates for the various X-bodies ensures that the recorded EXIF information reflects the actual aperture and focal length when the TC is used.

A 1.4x crop may not seem much, but all help is welcome with a 16Mpx sensor…

The combination of the 1.5x APS-C sensor crop factor and the 1.4x TC magnification results in a final ‘35mm FF equivalent’ focal length of 2.1x the original lens value.

At this moment, the XT 1.4x TC can only be used with the XF 50-140mm f/2.8 zoom. The combo becomes a 70-196mm f/4 zoom lens (covering the same angle of view as a full-frame 105-294mm lens). We can however expect additional compatibility with the XF 100-400mm super-tele zoom and XF 120mm macro lenses that will challenge our lens lust (and bank accounts) sometime during 2016.

The XF 1.4x TC sitting where it currently belongs: behind an XF 50-140mm tele zoom

There are countless reviews documenting how well the TC 1.4x/50-140 combination performs optically. Suffice to say that my own quick-and-dirty tests fully confirm this.

100% center crops with and without the 1.4x TC (click on image for larger version)

Besides any possible optical considerations, it is physically impossible to mount the TC to any other current XF lens. The front part of the TC extends significantly forward from the lens mount, and requires some ‘opens space’ at the back end of the to-be-mounted lens. Obviously, the design of the XF 50-140mm accommodates for this (and so will – at least – two of the future ones) but none of the other available XF lenses will work…

Now, if any other lens came with both an XF mount AND sufficient open space at the back to receive the TC’s protrusion, would it then be possible to make use of the teleconverter…?

Stage right: an adapted legacy lens

When I first saw images of the XF 1.4x TC and noticed its unusual shape (compared to traditional TC designs), I vaguely remembered a post I stumbled upon a few months earlier on a Micro Four Thirds forum. The Olympus M.Zuiko MC14 indeed has a very similar construction.

Ever since acquiring a Fujifilm X-Pro1 in early 2012, I have used a number of F-mount lenses collected over 40+ years of shooting with Nikon SLRs and DSLRs. In case you are interested: more info on this introduction to adapted lenses, and this full overview of Metabones adapters.

A mount adapter enables the use of ‘legacy’ lenses on recent system camera bodies. The classic (D)SLR design requires a fairly large flange (i.e. film/sensor-to-lens mount) distance to make room for the reflex mirror box. With mirrorless cameras, the lens mount sits a lot closer to the sensor. A basic lens adapter compensates for the difference by providing additional spacing between the respective lens mounts. For a Nikon F to Fujifilm X mount adapter, that distance must be exactly 28.8mm.

The above image clearly shows that the (otherwise hollow) adapter provides ample space to accommodate the TC’s extending front section. Once the adapter is attached, the TC sits well behind the F-mount and does no longer requires a specific lens construction.

Obviously, there will be no electrical communication possible between lens and camera body, and we will not have any actual lens and aperture information embedded in the EXIF data. Nothing different here compared to the ‘regular’ use of such a lens adapter. However, metering in A and M modes as well as all forms of manual focus assistance remain fully operational. Great to discover that a camera-with-TC does not get confused when no XF lens is attached!

Solving the mechanical compatibility of course does not guarantee that we can expect a great or even acceptable optical performance. We are combining components that were originally designed for use in totally different circumstances. I don’t know of any teleconverter design that was not optimized for a specific and limited range of (mostly tele) lenses. And I am pretty convinced that none of the Fujifilm engineers even for a brief moment worried about such an exotic line-up!

With that in mind, I was more than curious to have a look at my first test images. All ye who enter here, abandon hope…

First test: some ‘normal’ primes

I honestly did not have any expectations at all for this initial quick assessment. We all know that TCs are traditionally intended for use with tele lenses. So why even bother to snap on a cheap mid-80’s Nikon AF 50mm f/1.8 (pre-D) and a slightly more recent Nikon AF-D 85mm f/1.8?

Surprise!

Have a look at these images and 100% center crops, shot in my familiar light tent studio, at distances around 70cm resp. 100cm. For all of the comparison shots following, both versions have been processed with identical Lightroom settings. (click on any image for a larger version)

Nikon AF 50mm f/1.8 with XF 1.4x TC

100% center crops with TC, at f/1.8 resp. f/4

Nikon AF-D 85mm f/1.8 with XF 1.4x TC

100% center crops with TC, at f/1.8 resp. f/4

With a little stopping down, you get perfectly useable image quality (remember for exposure calculation that with the TC the actual aperture is one stop slower than set on the lens). No visible signs of vignetting or aberrations, in fact a very similar optical performance as the original ‘naked’ lens.

As the available range of Fujifilm XF lenses grows (with some additional gap fillers from third parties), my regular use of adapted lenses has substantially diminished. Except for a few ones, for which there are still no alternatives with an X-mount. So let’s have a look at two more legacy primes that frequently find themselves onto my X cameras.

Second test: a trusted macro lens

I bought a Tamron 90mm f/2.8 SP Di Macro lens (with Nikon F-mount) in 2004, and have used it extensively ever since. It is an extremely sharp lens, that offers a generous working distance even at extreme close-up range. The longer focal length, the 1:1 capability and the generous manual focus ring are three reasons for giving it ample show time next to my beloved XF 60mm. The only X-mount alternative is the Samyang 100mm f/2.8 Macro, but that one does not offer enough value added to consider a switch. So, for now the Tamron 90mm it is (until perhaps I give in to the XF 120mm?).

If this lens would still perform in combination with the XF 1.4x TC, it would bring an increased 1.4:1 magnification without sacrifying shooting distance.

The Tamron 90mm f/2.8 SP Di Macro ready for action

I will let you be the judge on the results of a quick macro test. I used reasonable care to make good shots (solid tripod, manual focus assist, electronic remote, self timer…) without spending too much effort. My subject was a 29mm x 25mm postage stamp; the actual width of the word ‘BELGIË' is 7.5mm, the circle around the ‘1’ has a 4mm diameter. As always, clicking on an image presents a larger version in a separate window.

Full image without TC

Full image with TC

100% center crops compared

There is a little loss of micro contrast, requiring nothing more than a small nudge to the Clarity slider. No sign of visible vignetting or serious corner sharpness degradation. My conclusion: whenever I hit the need for the extra magnification, I will not hesitate to put the XF 1.4x TC behind this lens!

I also did a quick test on a distant subject (about 150m from my shooting position):

Full image without TC

Full image with TC

100% center crops compared

A nice result as well.

Third test: a classic tele

I have always liked Nikon’s AF-D 180mm f/2.8 IF ED. I owned a neat second hand copy, sold it later (as I felt I wasn’t using it often enough on my D700) but ended up acquiring another used copy, one in even better condition. This medium tele lens is tack sharp even fully open, and has a nice micro contrast.

The 180mm + TC on an X camera delivers an angle of view close to a 400mm f/4 lens on a full-frame body. As expected, a stopping down 1 or 2 stops and adding a little Clarity leads to more than acceptable results. At f/2.8 this lens shows visible chromatic aberration; adding the TC makes it a little worse; by f/5.6 it is already significantly reduced. Again, nothing that Lightroom cannot easily correct for.

I next pointed my camera towards a subject at medium distance (some 25m):

Finally, I was curious about the close-up performance of the 180mm + 1,4x TC combination. I took the following shots from about 1m distance:

Full image without TC

Full image with TC

100% center crops (without and with TC) compared

Conclusion – and why bother?

All of the above is far from a stringent, carefully controlled optical test. Frankly, the whole idea of using the XF 1.4x TC in combination with an adapted legacy lens is a bit ‘exotic’ to begin with… and therefore perhaps not worth much more effort J

My experiments indicate that more than reasonable image quality can be obtained with a broad range of non-Fujifilm lenses. That by itself is a remarkable outcome, and probably points at a very ‘robust’ optical design of the teleconverter. If true, that offers the perspective for many more useful (and designed for) lens combinations in the future. How about that?

Beware to extrapolate my findings to any other TC/lens combinations! Please do realize that any decent result is nothing more than a collateral by-product of the TC ‘s design targets.

If you happen to own an XF 1.4x TC, as well as some legacy lenses and an adapter with sufficient physical depth, please go explore! You may discover a handy stopgap solution here and there, while we wait for an even more complete XF lens line-up. I have little doubt that I will still use these legacy lenses once the 120mm macro and a 100-400mm tele zoom become available (and part of my glass collection): in the long term autofocus and image stabilization will prevail, even when coming at the cost of one f-stop or so. But until then…

So why again do we even bother testing these weird combinations? Because we can, of course, and because it’s a lot of fun as well!